1. Field of the Invention
This invention relates to a fluorescence detecting system which detects fluorescence from the fluorescence agent information based on fluorescence from the fluorescence agent and/or auto-fluorescence information based on auto-fluorescence emitted from an object part upon projection of stimulating light onto an object part which has been dosed with a fluorescence agent in advance.
2. Description of the Related Art
There has been known a fluorescence detecting system which detects fluorescence emitted from an object part to use it for diagnosis of the tissue properties of the object part. For example, an fluorescence from the fluorescence agent detecting system is a system wherein tumor-affinity agent (e.g., ATX-S10, 5-ALA, NPe6, HAT-D01, Photofrin-2 or the like) which emits fluorescence upon excitation by light was dosed to an object in advance as a fluorescent agent to be absorbed by a part of tumor such as cancer, stimulating light in the exciting wavelength range of the agent is projected onto the part, fluorescence emitted from the agent (referred to as “fluorescence from the fluorescence agent”, hereinbelow) accumulated in the part of tumor is detected, and fluorescence from the fluorescence agent information reflecting the tissue properties of the object part is obtained from the fluorescence from the fluorescence agent and displayed. Or the localization and/or the infiltration of the part of tumor are determined by comparison and analysis of the fluorescence from the fluorescence agent information, and the result of determination is displayed.
Further, there has been known a fact that the intensity and the spectrum of the fluorescence emitted from the auto-fluorescence material in an object part (referred to as “auto-fluorescence”, hereinbelow) upon projection of stimulating light in a predetermined wavelength band onto the object part differs depending on whether the object part is of normal tissue or diseased tissue as shown in FIG. 9. There has been proposed an auto-fluorescence detecting system where, on the basis of this phenomenon, stimulating light in a predetermined wavelength band projected onto the object part and auto-fluorescence information reflecting the tissue properties of the object part is obtained from the auto-fluorescence and displayed or the localization and/or the infiltration of the part of tumor are determined by analysis of the auto-fluorescence information, and the result of determination is displayed. (For example, Japanese Unexamined Patent Publication No. 2002-172082)
The fluorescence detecting system of this type is generally incorporated in an endoscope, a colposcope or a microscope for surgery which are inserted into a body cavity. As a method of detecting the fluorescence, there have been known a method in which the fluorescence is two-dimensionally detected by the use of an image pick-up element such as a CCD and a method in which a fluorescence spectrum is obtained from a point on the object part by the use of a fiber and/or a spectroscope.
Further, there have been proposed various comparing/analyzing method in these fluorescence detecting systems in order for the observer to more accurately obtain information on tissue properties on the basis of fluorescence information.
When the stimulating light is projected onto an object part such as an organic tissue to image the intensity of fluorescence emitted from the object part as a fluorescence image and the fluorescence information obtained on the basis of the fluorescence image is displayed, the intensity of the stimulating light to be projected is not uniform due to the irregularities on the object part. When an auto-fluorescence image is to be taken, though the intensity of fluorescence emitted from a normal object part is substantially proportional to the illuminance of the stimulating light, the illuminance of the stimulating light is reduced in inverse proportion to square of the distance. Accordingly, the fluorescence received from a diseased tissue nearer to the light source is sometimes stronger than the fluorescence received from a normal tissue far away from the light source, which makes it infeasible to accurately determine the tissue properties of the object part only on the basis of information on the intensity of fluorescence.
In order to suppress such a problem, there has been proposed a method in which light different from the stimulating light in the wavelength band is projected onto the object part as reference light to detect the intensity of the reflecting light reflected at the object part illuminated by the reference light, and a fluorescence image based on the result of the division between the intensity of the fluorescence and the intensity of the reflecting light of the reference light is generated, that is, fluorescence information based on the difference of the light intensity of the fluorescence reflecting the tissue properties is obtained and displayed.
Further, in the case of the auto-fluorescence, since the fluorescence emitted from a normal object part and the fluorescence emitted from a diseased object part differ from each other in the shape of spectrum, there has been proposed a method in which an intensity ratio of two kinds of fluorescence obtained from different wavelength bands, e.g. a narrow band near 480 nm and a broad band from near 430 nm to near 730 nm is obtained by division and a fluorescence image based on the result of the division is displayed, that is, fluorescence information based on the difference of the shape of the spectrum of the fluorescence reflecting the organic tissue properties is obtained and displayed.
Further, this applicant has proposed a system in which stimulating light is projected onto an object part which has been dosed with a fluorescence agent to obtain the fluorescence from the fluorescence agent and the auto-fluorescence, and fluorescence information based on the fluorescence from the fluorescence agent and the auto-fluorescence is obtained. (Japanese Unexamined Patent Publication No. 9(1997)-308604)
Further, in “O plus E vol. 20, No. 7, pp. 836 to 840 (1998/7)”, it has been reported that the fluorescence emitted from the object organic body is differently absorbed and scattered in the organic body depending on the wavelength band as a result of detecting and analyzing the fluorescence emitted from the organic body point to point. It has been further reported that a distribution is generated in the incident angle of the stimulating light to the surface of an organic body due to irregularity on the surface of the object and the degree of absorption or scatter changes, and the intensity of fluorescence obtained changes depending on the distance between the measuring system and the object. These influences distort the spectrum of the fluorescence obtained by the detector from the spectrum of the fluorescence originally emitted from the object.
In the technology disclosed in the above “O plus E vol. 20, No. 7, pp. 836 to 840 (1998/7)”, a spectrum of light reflected at the surface of an organic body is detected and the distortion of the spectrum of fluorescence is corrected by the use of the spectrum of the reflected light. Further, this applicant has proposed a method in which reflected light the same in the wavelength band as the fluorescence to be obtained is obtained and fluorescence information where the distortion of the spectrum of fluorescence is corrected is obtained by the use of the reflected light.
Recently, technology of detecting fluorescence is improved and even very weak fluorescence becomes able to be detected. As a result, it has been found that the fluorescence from the fluorescence agent information obtained on the basis of the fluorescence from the fluorescence agent includes highly accurate information on the localization and/or the infiltration of the part of tumor and the auto-fluorescence information obtained on the basis of the auto-fluorescence includes slightly less accurate information on the localization and/or the infiltration of the part of tumor. That is, it can be said that there is a slight deviation between the auto-fluorescence information obtained on the basis of the auto-fluorescence and the fluorescence from the fluorescence agent information obtained on the basis of the fluorescence from the fluorescence agent. Accordingly, it is preferred that both the fluorescence from the fluorescence agent information and the auto-fluorescence information be obtained in order to know the tissue properties more accurately.
In Japanese Unexamined Patent Publication No. 9(1997)-308604 described above, stimulating light is projected onto the object part which has been dosed with a fluorescence agent and the fluorescence from the fluorescence agent and the auto-fluorescence are obtained. However, since the fluorescence from the fluorescence agent wavelength band and the auto-fluorescence wavelength band mingle with each other, it is impossible to discretely obtain the auto-fluorescence information based on the auto-fluorescence and the fluorescence from the fluorescence agent information based on the fluorescence from the fluorescence agent.
Though it is possible to discretely obtain the auto-fluorescence information and the fluorescence from the fluorescence agent information by obtaining the auto-fluorescence before the object part is dosed with a fluorescence agent and obtaining the fluorescence from the fluorescence agent after the object part is dosed with a fluorescence agent, this is disadvantageous in that load on the examinee is increased, for instance, the examination is elongated, and identification of the object part becomes difficult.